Ingestion and killing of bacteria by polymorphonuclear neutrophils is an important part of the normal host defense against bacterial infection. The principal investigator plans to continue studies concerning normal mechanisms as well as studies with gonococci with special emphasis on the surface attachment of the piliated organisms. We will study the morphology of this attachment and try to determine the anatomy of the receptors for the gonococcal pili. We will pursue investigations with leukototoxic streptococci with special attention to the ability of leukocytes to kill these organisms (in addition to the well known leukotoxic effect of the streptococci). Leukocytes have the ability to kill multicellular parasites and we will continue our studies with Trichomonas vaginalis and extend our observations made with Entamoeba hostolytica. Virulent strains of Entamoeba histolytica have the ability to kill keukocytes while avirulent strains are rapidly killed by the neutrophils. Monocytes from patients with chronic granulomatous disease transform into macrophage like cells in culture. We are examining the ability of these cells to kill microbes.